SR meaning in Maths ?

The slide rule is a mechanical analog computer. As a graphical analog calculator, the slide rule is closely related to a nomogram; the former is used for general calculations, the latter for application-specific computations.

The slide rule is used primarily for multiplication and division, and also for functions such as exponents, roots, logarithms, and trigonometry, and typically not for addition or subtraction. Though similar in name and appearance to a standard ruler, the slide rule is also not meant to be used for measuring length or drawing straight lines.

Slide rules exist in a diverse range of styles and generally appear in a linear or circular form with slide rule scales inscribed with standardized graduated markings essential to performing mathematical computations. Slide rules manufactured for specialized fields such as aviation or finance typically feature additional scales that aid in calculations particular to those fields.

At its simplest, each number to be multiplied is represented by a length on a sliding ruler. As the rulers each have a logarithmic scale, it is possible to align them to read the sum of the logarithms, and hence calculate the product of the two numbers.

The Reverend William Oughtred and others developed the slide rule in the 17th century based on the emerging work on logarithms by John Napier. Before the advent of the electronic calculator, it was the most commonly used calculation tool in science and engineering. The slide rule's ease of use, ready availability, and inexpensiveness caused its use to continue to grow through the 1950s and 1960s even as computers were being gradually introduced. The introduction of the handheld electronic scientific calculator around 1974 made them largely obsolete and most suppliers left the business.